06/26/2009 FCST: NE,SD,ND,IA,MN

[Derrick Herndon]

In line with the SPC Day 2 Outlook I thought I would start a thread for tomorrows setup. It looks like there will be at least 2 potential targets for tomorrow. One is along the well defined boundary fcst to lie from near the Central SD/ND border extending SE into IA. The other is ahead of an approaching mid-level speed max in Central NE. The warm front target has the advantage of better sfc convergence near the triple point with an associated increased confidence in convection. The Nebraksa target is more conditional but perhaps more likely to yield discreet storms early on. The NAM and GFS paint a nice combination of CAPE and 1 km SRH over Central NE tomorrow afternoon. Add in the speed max and this seems like a pretty good setup. The 2 downsides are possible convection early in the day and warm mid level temps. An early target would be near O'Neill, NE where models shows modestly backed surface flow and some nicely curved hodos.

 

[Mike Hollingshead]

The GFS has a sick shear profile over NE with that disturbance kicking out in the late afternoon.

http://beta.wxcaster.com/models/GFS/CENTRAL/CENTRAL_GFS_500_GPHVORT_36HR.gif

over

http://beta.wxcaster.com/models/GFS/CENTRAL/CENTRAL_GFS_850_GPHTMPWIND_36HR.gif


Looks like perhaps morning convection on the NE/KS border is messing with the instability over parts of central/eastern NE tomorrow. The NAM was placing really warm low levels and high LCLs over this whole region. If that can be worked out with that wave coming out or the more backed low levels on the GFS, one would think NE could be rather rewarding tomorrow. Pretty big differences between the two models in that regard though, with the NAM not making NE look too interesting to me.

 

[Michael O'Keeffe]

I agree with Mike, but I am really liking what the NAM did with the 18z. It brought in much stronger 500mb winds and nice SE LLJ similar to the GFS. The hodographs near O'Neill, NE look sick for tomorrow at 0z. Now lets hope this trend continues on the 0z because if it does Nebraska looks under the gun again!

O'Neill, NE Sounding

 

[Mike Hollingshead]

I agree with Mike, but I am really liking what the NAM did with the 18z. It brought in much stronger 500mb winds and nice SE LLJ similar to the GFS. The hodographs near O'Neill, NE look sick for tomorrow at 0z. Now lets hope this trend continues on the 0z because if it does Nebraska looks under the gun again!

O'Neill, NE Sounding

You beat me to it. Was just going to post the same sounding. Here it is on Earl's which I still like a bit better than Twister Data's just because all that other info is there with it: O'Neill 18z Nam


Nothing like a big ol bullseye.

http://www.wxcaster2.com/CENTRAL_MESO-ETA_SVR_CAPESRHSWEAT_30HR.gif

0-1km EHI of 10!

http://beta.wxcaster.com/models/meso-eta/central/CENTRAL_ETA212_0-1KM_EHI_30HR.gif

First thought that comes to my mind is June 9, 2003, but of course there are differences(like way cooler aloft). I could see a similar storm situation as the O'Neill one that time around. A bit on the high based side, but a beast....one of the meanest looking things I've seen. There, now it's firmly jinxed.

 

[Bill Schintler]

Storm Chasing Target for Friday, June 26

Chase target:
O'Neill, NE

Timing and storm mode:
Storms will expand in coverage through 4 PM CDT. Primary storm mode will be multicells with embedded supercells.

Synopsis:
The main band of westerlies will remain over the northern tier of states while the upper low over CA opens up and ejects an impulse, which will track through NEB and then IA and MN. This shortwave will aid in assent and removal of CIN by mid-afternoon.

Discussion:
Convection is ongoing over northeastern CO and western NEB; apparently associated with a mid-level impulse and strengthening LLJ. Precipitation and associated cloud cover will exist over NEB in areas N of I-80 during the morning hours. Low pressure will organize in the Goodland, KS area by late afternoon; with a WF extending SE from an inverted trough along a Valentine to Lincoln line. Moderate instability will develop as mid-level lapse rates in excess of 9C/km overspreads LLVL dewpoints approaching 75F. Backed SFC flow will exist N and E of the boundary, with LLVL directional shear will increasing during the evening hours as an veering LLJ increases to 50 kts. Deep-layer shear will increase to nearly 50kts as the aforementioned shortwave overspreads the area.

- Bill
KD0DJG
www.twistertoursusa.com
9:52 PM CDT, 06/25/09

 

[Craig McPeck]

Best shear, instability and moisture will be around the northern nebraska area. Will be heading out to Oneill Nebraska for Friday! A moderate risk seems possible with the next outlook.

 

[Chris Hovanic]

Provided the morning MCS can clear out in time, and allow for sufficient heating along the convective outflow-enhanced warm front, today holds great potential. I'm currently on a mid-shift and get off at 9:30am, will be leaving Kansas City at that time for Bassett, NE along with fellow co-workers Brian Koochel and Renee Geiser.

Regarding the forecast, I have concerns that the MCS could linger into the early afternoon hours given that the mid-level shortwave responsible is somewhat "stuck under the ridge" and meanders slowly E-NE. If this happens, the northward progression of the warm front will be halted, thereby keeping it further south across central and north-central Nebraska, in closer proximity to the mid-level thermal ridge axis categorized by +12 to +13C 700mb temperatures. If this occurs, there could be significant capping issues and the potential for convective initiation along the warm front would be drawn into question.

Provided storms can manage to develop in the vicinity of the warm front in the late afternoon/early evening hours, they should quickly become supercellular as deep-layer shear strengthens significantly as the next mid-level shortwave/attendant jet max notches northeast atop the low-level southeasterly flow. Sustained supercells near the warm front should produce tornadoes, some perhaps strong thanks to the incredible low-level speed and directional shear in place.

Good luck to all those out!

 

[Andrea Griffa]

While taking a quick look at the latest Ruc run I've seen a very nice improving in low level shear. I'm quite impressed by the low level jet to the S-SE forecasted between 35 and 50 knots that could enhance low level helicity.
Not to mention the high dews, high cape, low LCLs and a nice mid/high level shear. I don't see an unbreakable cap. I would increase tornado risk to 10 per cent today.
I would start from Billsburg,SD. Good luck to all of you chasing today.